Many hardwired communications systems use plug-jack connectors to connect a communications cable to another communications cable or to a piece of equipment such as a computer, printer, server, switch or patch panel. By way of example, high speed communications systems routinely use such plug-jack connectors to connect computers, printers and other devices to local area networks and/or to external networks such as the Internet. FIG. 1 depicts a simplified example of such a hardwired high speed communications system that illustrates how plug-jack connectors may be used to interconnect a computer 1 to, for example, a network server 10.
As shown in FIG. 1, the computer 1 is connected by a cable 2 to a communications jack 5 that is mounted in a wall plate 9. The cable 2 is a patch cord that includes a communications plug 3, 4 at each end thereof. Typically, the cable 2 includes a plurality of wire conductors (e.g., eight), which are arranged in pairs so that each pair of conductors may carry a separate differential signal. Communications plug 3 inserts into a communications jack (not pictured in FIG. 1) provided in the back of the computer 1. Communications plug 4 inserts into an opening or “plug aperture” 6 in the front side of the communications jack 5 so that the contacts of the communications plug 4 mate with respective contacts of the communications jack 5 (if the cable 2 includes eight conductors, the communications plugs 3, 4 and the communications jack 5 will typically each have eight contacts). The communications jack 5 includes a wire connection assembly 7 at the back end thereof that receives a plurality of conductors (e.g., eight) from a second cable 8 that are individually pressed into slots in the wire connection assembly 7 to establish mechanical and electrical connections between each conductor of the second cable 8 and a respective one of a plurality of conductive paths through the communications jack 5. The other end of the second cable 8 is connected to a network server 10 which may be located, for example, in a telecommunications closet of a commercial office building. Thus, the patch cord 2, the cable 8 and the communications jack 5 provide a plurality of electrical paths (e.g., four differential signal paths) between the computer 1 and the network server 10. Each of these electrical paths may be used to communicate electrical information signals between the computer 1 and the network server 10. It will be appreciated that typically one or more patch panels or switches, along with additional communications cabling, would be included in the electrical path between the second communications cable 8 and the network server 10. However, for ease of description, these additional elements have been omitted from FIG. 1 and the second communications cable 8 is instead shown as being directly connected to the network server 10.
In order to provide standardization between the high speed communications equipment marketed and sold by different vendors, industry standards documents have been promulgated that specify various mechanical and electrical properties for communications jacks and plugs. One example of such a standard is the TIA/EIA-568-B.2-1 standard that was approved on Jun. 20, 2002 by the Telecommunications Industry Association. These industry standard documents typically incorporate, by reference, interface and wiring standards that specify, among other things, the dimensions and configurations of various types of standardized communications plugs and jacks so that industry standards-compliant plugs and jacks sold by different vendors will work with each other.
By way of example, the above-referenced TIA/EIA-568-B.2-1 standard requires compliance with interface specifications set forth in the FCC Part 68.500 document, which defines, among other things, the dimensions and configurations for various plug-jack interfaces, including plugs and jacks that conform to the Registered Jack 45 (“RJ-45”) wiring standard and plugs and jacks that conform to the Registered Jack 11 (“RJ-11”) wiring standard. The RJ-45 wiring standard describes wiring specifications for eight wire connector assemblies (including plugs and jacks) that are commonly used, for example, in Ethernet networks to connect computers and other hardware to local area networks (LAN) and/or the Internet, as is discussed above with respect to FIG. 1. The RJ-11 wiring standard, on the other hand, describes wiring specifications for four and six wire connector assemblies that are used in the United States primarily to connect telephone equipment. Herein, a plug or jack that substantially complies with the RJ-11 wiring standard is referred to as an “RJ-11” or “RJ-11 style” communications plug or jack, and a plug or jack that substantially complies with the RJ-45 wiring standard is referred to as an “RJ-45” or “RJ-45 style” communications plug or jack.
FIG. 2A is a simplified perspective view of an RJ-45 style communications jack 20, and FIG. 2B is a simplified plan view of an RJ-45 style communications plug 30. FIG. 4 is a perspective view of the RJ-45 style communications plug 30. As shown in FIG. 2A, RJ-45 jack 20 includes eight resilient jackwire contacts 21-28, which are mounted so that they extend into a plug receiving cavity 29. As shown in FIGS. 2B and 4, the RJ-45 communications plug 30 includes eight plug contacts 31-38, which are often referred to as “blades.” The plug contacts 31-38 are received within contact slots 31′-38′ that are provided in the top surface of the housing 39 of RJ-45 communications plug 30 (each contact slot 31′-38′ also extends into the front surface of RJ-45 communications plug 30). The contact slots 31′-38′ on RJ-45 communications plug 30 are positioned so that when the plug 30 is inserted into RJ-45 communications jack 20, the contact slots 31′-38′ are aligned with plug contact regions of respective ones of jackwire contacts 21-28. Thus, when the RJ-45 communications plug 30 is inserted into the plug receiving cavity 29 of RJ-45 communications jack 20, the plug blades 31-38 make mechanical and electrical connection with respective ones of the jackwire contacts 21-28. The plug-jack interface is designed so that, as the plug 30 is inserted into plug receiving cavity 29, the blades 31-38 of the RJ-45 communications plug 30 engage their respective contacts 21-28 and deflect them back and/or upward a short distance. The resiliency of the jackwire contacts 21-28 creates a “contact force” that holds the jackwire contacts 21-28 in firm engagement with their respective plug blades 31-38. When the RJ-45 communications plug 30 is removed, the jackwire contacts 21-28 move downwardly and/or forwardly back into their normal resting position.
FIG. 3A is a simplified perspective view of a six contact RJ-11 communications jack 40, and FIG. 3B is a simplified plan view of a six contact RJ-11 communications plug 50. As shown in FIG. 3A, the RJ-11 communications jack 40 includes six jackwire contacts 42-47, which are mounted so that they extend into a plug receiving cavity 49. As shown in FIG. 3B, the RJ-11 communications plug 50 includes six plug contacts 52-57. The plug blades 52-57 are received within contact slots 52′-57′ on the top surface of the housing 59 of RJ-11 communications plug 50. The contact slots 52′-57′ on RJ-11 communications plug 50 are positioned so that when the plug 50 is inserted into RJ-11 communications jack 40, the contact slots 52′-57′ are aligned with plug contact regions of respective ones of the jackwire contacts 42-47. The RJ-11 communications plug 50 and jack 40 work together in the same manner, described above, that the RJ-45 communications plug 30 and jack 20 work together. An RJ-11 communications plug with four contacts does not contain contacts 52 and 57, but does include the contact slots 52′ and 57′. As the differences between four contact and six contact RJ-11 plugs are immaterial to this description, the remainder of this specification will focus on six contact RJ-11 communications plugs.
As is evident from FIGS. 2-4, RJ-45 connector assemblies (i.e., plugs and jacks) look very similar to RJ-11 connector assemblies, except that RJ-45 communications plugs and jacks are slightly wider than RJ-11 communications plugs and jacks and include at least two more contacts. Moreover, telephone and facsimile lines that are wired using RJ-11 style communications plugs and jacks are often located in the telecommunications closet of a building in close proximity to Ethernet equipment that is wired using RJ-45 plugs and jacks. Due to the visual similarities between the RJ-11 and RJ-45 connector assemblies, and their close proximity in many telecommunications closets, all too often, the slightly narrower RJ-11 communications plugs are inserted into RJ-45 communications jacks.
Unfortunately, when an RJ-11 communications plug is inserted into an RJ-45 communications jack, the RJ-45 communications jack can be damaged. This can best be seen with reference to FIG. 5, which is a cross-sectional diagram taken along line 5-5 of FIG. 4. As shown in FIG. 5, the vertical height of the housing 39 of plug 30 is about 0.260″. However, the plug blades 31-38 that are mounted in the contact slots 31′-38′ do not extend all the way to the top of housing 39. Accordingly, the effective height of the housing 39 along respective ones of the contact slots 31′-38′ is somewhat less (approximately 0.023″ less) than the height of the housing 39. The same is true with respect to the RJ-11 plug 50 of FIG. 3B, namely the height of the housing 59 of plug 50 is approximately 0.260″, while the distance from the top edge of each plug blade 52-57 to the bottom of the housing 59 is only about 0.237″.
When RJ-11 communications plug 50 is inserted into RJ-45 communications jack 20, the forward and top surfaces of the housing 59 of the plug 50 engage jackwire contacts 21 and 28 of jack 20, as the six blade RJ-11 communications plug 50 does not include contact slots or plug blades in the outside two contact positions (i.e., the major difference between the six contact RJ-11 communications plug 50 and the RJ-45 communications plug 30 is that the RJ-11 communications plug 50 does not include slots 31′ and 38′ and contacts 31 and 38 that are included on the RJ-45 communications plug 30). As the housing 59 of RJ-11 communications plug 50 (as opposed to contacts of plug 50), which has the full height of 0.260″, engages the outside jackwire contacts 21 and 28, the jackwire contacts 21 and 28 of jack 20 are over-deflected by 0.023″ when RJ-11 communications plug 50 is accidentally inserted into RJ-45 communications jack 20 (as compared to when an RJ-45 plug is inserted). Unless the jackwire contacts 21 and 28 of jack 20 are specially designed to accommodate this additional amount of deflection, the jackwire contacts 21 and 28 may become permanently set in this over-deflected position if RJ-11 communications plug 50 is inserted into RJ-45 communications jack 20 (i.e., the contacts lose some or all of their ability to spring back into their resting position). If this occurs, when an RJ-45 communications plug 30 is later inserted into the RJ-45 communications jack 20, the “contact force” needed to keep blades 31 and 38 of the RJ-45 communications plug 30 in abutment with the respective jackwire contacts 21 and 28 of the RJ-45 communications jack 20 may not be present (or may be insufficient), which may result in poor performance. When insufficient contact force is present, the RJ-45 communications jack 20 may also fail to pass certain tests in the industry standards such as, for example, a specified minimum contact resistance that must be maintained between each plug blade and its respective jackwire contact after a minimum number of plug insertions and removals and under various environmental conditions (e.g., temperatures, relative humidity, etc.).